diff --git a/ci/tests/test_geneformer/test_geneformer_model.py b/ci/tests/test_geneformer/test_geneformer_model.py
index d029aa9b..fd6a2e9b 100644
--- a/ci/tests/test_geneformer/test_geneformer_model.py
+++ b/ci/tests/test_geneformer/test_geneformer_model.py
@@ -52,7 +52,8 @@ def test_ensure_data_validity_raising_error_with_missing_ensembl_id_column(self,
     
     @pytest.mark.parametrize("gene_symbols, raises_error",
                              [
-                                (['ENSGSAMD11', 'ENSGPLEKHN1', 'ENSGHES4'], True),
+                                (['ENSGSAMD11', 'ENSGPLEKHN1', 'ENSGHES4'], True), # humans
+                                (['ENSMUSG00000021033', 'ENSMUSG00000021033', 'ENSMUSG00000021033'], True), # mice
                                 (['SAMD11', 'None', 'HES4'], True),
                                 (['SAMD11', 'PLEKHN1', 'HES4'], False),
                              ]
diff --git a/helical/models/geneformer/model.py b/helical/models/geneformer/model.py
index 5ca23f78..b7139b78 100644
--- a/helical/models/geneformer/model.py
+++ b/helical/models/geneformer/model.py
@@ -145,7 +145,7 @@ def process_data(self,
 
         # map gene symbols to ensemble ids if provided
         if gene_names != "ensembl_id":
-            if (adata.var[gene_names].str.startswith("ENSG").all()) or (adata.var[gene_names].str.startswith("None").any()):
+            if (adata.var[gene_names].str.startswith("ENS").all()) or (adata.var[gene_names].str.startswith("None").any()):
                 message = "It seems an anndata with 'ensemble ids' and/or 'None' was passed. " \
                 "Please set gene_names='ensembl_id' and remove 'None's to skip mapping."
                 LOGGER.info(message)